Electric circuit breaker with voltage-controlling resistances and means for switching the resistances in synchronism



June 25, 1968 R WLLER 3,390,239

- ELECTRIC CIRCUlT BREAKER WITH VOLTAGE-CONTROLLING RESISTANCES AND MEANS FOR SWITCHING THE RESISTANCES IN SYNGHRONISM Filed Feb. 23, 1965 6 Sheets-Sheet l INVENTOR. R/cHARD H. MILLER,

5 Mam-w mm A 7'7'0RNE Y June 25, 1968 pv r, 390,239

ELECTRIC CIRCUIT BREAKER WITH VOLTAGECONTRQLLING' RESISTANCES Ann MEANS FOR-SWITCHING Sheets-S THE RESISTANCES IN SYNCHRONISM het Filed Feb. 23, 1965 v INVENTOR Flag-MR0 H. MILLER,

ATTORNEY June 25, 1968 R. H. MILLER ELECTRIC CIRCUIT BREAKER WITH VOLTAGE-CONTROLLING RESISTANCES AND MEANS FOR SWITCHING THE RESISTANCES IN SYNCHRONISM Filed Feb. 23, 1965 6 Sheets-Sheet 5 INVENTOR. R/CHARD H. MILLER,

ATTORNEY June 25,1968 R H. MILLER 3 3,390,239

ELECTRIC CIRCUIT BREAKER WITH VOLTAGE'CONTROLLING RESISTANCES AND MEANS FOR SWITCHING THE RESISTANCES IN SYNCHRONISM Filed Feb. 23, 1965 6 Sheets-Sheet 4 INVENTOR. RICHARD H. MILLER,

M m m,

ATTORNEY June 25, 1968 R. H. MILLER 3,390,239

ELECTRIC CIRCUIT BREAKER WITH VOLT CONTROLLING ESISTANCES D ME 8 NG THE RESIST ES S HRONI Filed Feb. 23, 1965 6 Sheets-Sheet 5 3; 1 g 1 Q% X I a I 1% Mi fiw LI Z J /N VENTOR.

RICHARD H. MILLER,

ATTORNEY 6 Sheets-Sheet 6 //v VENTOR H/cHA/w H. MILLER, Macaw M A 77'0RNEY R. H. MILLER THE RESISTANGES IN SYNGHRONISM I I I E I I I I I I I I I I I I l I I June 25, 1968 ELECTRIC CIRCUIT BREAKER WITH VOLTAGE-CONTROLLING RESISTANCES AND MEANS FOR SWITCHING Filed Feb. 25, 1965 u I I United States Patent ELECTRIC CIRCUIT BREAKER WITH VOLT- AGE-CONTROLLING RESISTANCES AND MEANS FOR SWITCHING THE RESISTANCES IN SYNCHRONISM Richard H. Miller, Berwyn, Pa., assignor to General Electric Company, a corporation of New York Filed Feb. 23, 1965, Ser. No. 434,270 21 Claims. (Cl. 200-146) ABSTRACT OF THE DISCLOSURE Discloses a circuit breaker comprising spaced-apart high voltage tanks, main breaks within the tanks, resistors respectively shunting the main breaks, and resistor switches within the tanks respectively connected in series with the resistors. Also within the tanks are controls for the respective resistor switches which are mechanically tied together through a linkage system both during circuit-breaker-opening and circuit-breaker-closing. Operation of this linkage system is controlled from a controlling point at ground potential; and at an intermediate point during an operating stroke of the linkage system, operation of the main breaks is initiated by the linkage system.

This invention relates to an electric circuit breaker of the type that is provided with a voltage-controlling resistor shunting its main contacts and a resistor switch for interrupting the current flowing through the resistor after the main contacts have been opened during a circuit-interrupting operation.

For controlling the voltage-developed across the main contacts of a high voltage circuit breaker during a circuit interrupting operation, it has been customary to shunt these contacts with a resistor through which current is transferred when the main contacts are opened to interrupt the circuit. For interrupting the current through the resistor, there is customarily provided a resistor switch having separable contacts connected in series with the resistor and in shunt with the main contacts.

In order for the resistor consistently to carry out its intended function, it is important for the resistor switch to open at a precisely controlled instant, occurring shortly after the main contacts have been opened. This requirement for precise timing in the opening of the resistor switch is especially stringent where there are a plurality of these resistor switches connected in series in a high voltage circuit. -In such an application, it is important that all of the resistor switches be opened substantially simultaneously in order to distribute across all of the resistor switches the high magnitude recovery voltage developed during interruption of the resistor current. If this high magnitude recovery voltage is im pressed across only a single resistor switch, which may have opened prematurely, it could cause a delayed breakdown, or restrike, across the open resistor switch which could lead to the development of excessive overvoltages. For reasons which will .be explained later, obtaining the desired synchronization of the resistor switches is par ticularly difiicult during those opening operations that immediately tel-low a closing operation.

Accordingly, an object of my invention is to provide means for controlling the resistor switches of a plurality of series-connected interrupting assemblies in such a "ice manner that their opening operations are synchronized with a high degree of precision, even during those circuit breaker opening operations that immediately follow a closing operation.

Another object is to provide a resistor switch that readily lends itself to precise control of the instant at which its contacts part and also to precise synchronization of its opening operation with the opening operation of other similar switches.

The requirement for synchronization of the seriesconnected resistor switches becomes even more diliicult to meet when the circuit breaker is rated for very high speed interrupting performance, for example, two cycles of 60 c.p.s. alternating current.

Another object of the invention is to provide an operating control for the resistor switches that can meet the synchronization requirements imposed by such high speed interrupting ratings, even for those opening operations that immediately follow a closing operation.

In certain circuit breaker applications, it is highly desirable that, during closing, the resistor shunting the main contacts be inserted into the power circuit at a precisely controlled instant prior to closing of the main contacts. Where there are a plurality of series-connected resistor switches in a very high voltage circuit, it is important that all of the resistor switches be closed substantially simultaneously. Otherwise, the inter-contact gap of the last resistor switch to close may be so long that it does not immediately break down in response to the high voltage developed thereacross when the other resistor switches close. This high voltage could cause a damaging arc-over across insulation paralleling this inter-contact gap that is last closed. To minimize the chances for such a damaging arc-over, it is important that the closing of the resistor switches be synchronized with a high degree of precision.

Accordingly another object of the invention is to provide means for closing the resistor switches with a high degree of synchronisrn and at such a point in. a closing operation that the resistors are inserted into the power circuit before the main contacts close.

Still another object is to provide a resistor switch in which the amount of delay preceding actual contact opening can be adjusted Without aifecting its closing time characteristics.

An additional object is to provide means for controlling the resistor switches of a polyphase circuit breaker in such a manner that the resistor switches in the respective phases of the breaker are synchronized with a high degree of precision.

In carrying out my invention in one form, I provide a circuit interrupting assembly that comprises a tank at a high voltage with respect to ground. The interrupting assembly further comprises a main break located within the tank, a resistor shunting the main break, and a resistor switch located within the tank having a break in series with the resistor and in parallel with the main break. The resistor switch break comprises a pair of separable contacts, one of which is movable and is urged toward an open position by opening bias means. A latch located within the tank is provided for restraining the movable contact in its closed position and is releasable to permit the opening bias means to drive the movable contact toward open position. The latch is controlled by latch-releasing means comprising a controlling member within the tank and a mechanical linkage coupled to the controlling member and extending to a control point at ground potential. When this linkage is actuated, the controlling member is driven through a predetermined stroke that produces release of the latch and resultant opening of the resistor switch. The main break is controlled by operation-initiating means, such as a pilot-valve, that is operable in response to actuation of said linkage to initiate an opening operation of the main break. Main breakoperating means responds to operation of the operationinitiating means to open the main break at a point sub stantially prior to separation of the resistor switch contacts.

The latch-releasing means is operable to cause opening of the resistor switch at a time after said linkage is first actuated that is independent of the speed at which the main break-operating means opens the main break.

In a further form of the invention, I provide a circuit breaker which comprises two spaced-apart interrupting assemblies constructed as described in the two immediately-preceding paragraphs. The tanks of the two assemblies are at different voltages with respect to each other. Common actuating means for the two linkages of the two interrupting assemblies is provided, and means comprising a mechanical interconnection between the two linkages is provided for causing the common actuating means to actuate said linkages substantially simultaneously, thereby producing substantially simultaneous opening of the two resistor switches.

For a better understanding of the invention, reference may be had to the following description taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a side elevational view partly in section and partly schematic showing a circuit-interrupting assembly embodying one form of the invention. This assembly includes a resistor switch.

FIG. 2 is a schematic showing of certain portions of the interrupting assembly of FIG. 1 and certain additional mechanism that is connected thereto. A portion of FIG. 2 is a view of the resistor switch in closed position taken along the line 22 of FIG. 1.

FIG. 3 is a schematic showing similar to that of FIG. 2 except showng the parts in the positions occupied when the resistor switch is open.

FIG. 4 is a perspective view of the resistor switch, taken when the resistor switch is in its closed position of FIGS. 1 and 2.

FIGS. 5 is a schematic sectional view taken alOng the line 5-5 of FIG. 1.

FIG. 6 is a schematic showing of two interrupting assemblies of the type shown in FIG. 1 mechanically connected together for operation in unison.

FIG. 7 is a circuit diagram illustrating the electrical power circuit through the two interrupting assemblies of FIG. 6.

General description of interrupting portion of circuit breaker studs carries a suitable stationary contact assembly 16 at its inner end. Cooperating with each stationary contact assembly is a movable contact 28 pivotally supported on a stationary pivot 29. These pivots 29 are supported upon stationary brackets 31 which are integral with one end of a stationary operating cylinder 32. Suitable means (not shown) are provided for transferring current between the movable contacts 28 and the brackets 31 so that the brackets 31 together with the cylinder 32 form a conductive path electrically interconnecting the two movable contacts 28. Thus, the two pairs of contacts 16, 28 are electrically connected in series between the two studs 15 and 20.

The cylinder 32, at its upper end, is suitably supported from a generally cylindrical housing 33, which, in turn, is suitably secured at its upper end to the metallic tank 12. Thus, when the contacts 16, 28 are closed, the tank 12 is at the same high voltage as the power circuit through the tank. When the circuit breaker is open, the conductive parts 28, 33 and 12 are electrically isolated from the two conductive studs 15 and 20. Suitable voltage distributing means (not shown) is provided for maintaining the tank 12 at an approximate mid-potential with respect to the studs 15 and 20 when the circuit breaker is in open position.

When the contacts 28 are moved out of engagement with their respective stationary contact 16, a pair of arcs are respectively formed at the two resulting breaks. For extinguishing these two arcs, a blast of the pressurized arc-extinguishing gas is caused to flow through each arcing region. The blast through each arcing region follows a path from the interior of the tank 12 through a normally-closed, but then-open, annular exhaust passage 36, which leads from the interrupting chamber 11 to the surrounding atmosphere. This path is indicated by the arrows e of FIG. 1. The housing 33 at its lower end is formed with a pair of generally diametrically-opposed nozzle-type electrodes 38 defining inlets to the exhaust passage 36 adjacent each pair of contacts. For controlling the flow of arc-extinguishing gas through the nozzle electrodes 38 and through the exhaust passage 36, there is provided at the upper end of the exhaust passage 36 a cylindrically-shaped reciprocable blast valve member 40. This blast valve member 40 slides smoothly in a surrounding tubular housing 41 integrally formed with the housing 33. In FIG. 1 the valve member 40 is shown in its closed position wherein its upper end sealingly abuts against the stationary valve seat 43. The movable valve member 40 is normally maintained in its closed position of FIG. 1 by the action of a suitable spring (not shown) and by the action of the pressurized gas in the passageway 36. This pressurized gas produces an unbalanced force on the movable valve member 49 that urges it upwardly into its closed position of FIG. 1.

Since the chamber 11 is normally filled with pressurized gas, it will be apparent that when the valve member 40 is opened by downward motion (by means not shown) pressurized gas in the chamber 11 will flow at high speed through the nozzles 38 and out passage 36 past the valve member 40 to atmosphere, as indicated by the arrows e of FIG. 1. This rapid flow of gas through the nozzles 38 creates an axial arc-enveloping blast which acts rapidly to extinguish the arcs which are drawn adjacent the nozzles by contact separation.

Operating mechanism for blast valve and main contacts For operating the blast valve 40 and the movable contacts 28, a combined operating mechanism preferably of the fluid-actuated type shown and claimed in application S.N. 42l,776-Miller and Beatty, filed Dec. 29, 1964, and assigned to the assignee of the present invention, is provided within the cylinders 32 and 33. Most of the details of this operating mechanism form no part of the present invention, and to simplify the present application, such details have not been shown in the drawing. A brief explanation of this mechanism will, however, be given in. order to facilitate an understanding of the present inven tion. Referring to FIG. 1, it will be noted that a pilot valve 51 is provided, and this pilot valve 51 is controlled by a pilot valve operating rod 52 coupled to the pilot valve 51 through a releasable coupling 53. The pilot valve 51 is normally closed, but when the operating rod 52 is driven downwardly, it acts through the releasable coupling 53 to open the pilot valve. This pilot valve opening admits pressurized air from the chamber 11 into the operating mechanism (not shown) to cause the operating mechanism to move the movable blast valve member 40 and the contacts 28 into their respective open positions. After a predetermined period sufficient for the arcs resulting from a contact-opening to be extinguished by the blast produced by blast valve-opening, the releasable coupling is disabled. This causes the pilot valve to immediately close. This, in turn, causes an immediate closure of the blast valve member 40. The movale contacts 28 are, however, held in their open position by a main latch 55 that becomes operative when the contacts have reached their fully open-position. The air pressure in the tank exerts a closing force on the movable contacts 28, but so long as the main latch 55 is in its latching position, this closing force cannot drive the contacts 28 closed. A circuit breaker closing operation is effected by releasing the main latch 55 to permit this closing force to drive the main contacts closed.

The force for effecting the above-described contactopening motion is transmitted to the contacts 28 through a crosshead 59 and a pair of links 60. Each of the links 60 is pivotally connected at its respective opposite ends to the crosshead 59 and one of the contacts 28, as is in(li cated at 61 and 62. The crosshead 59 is mounted for reciprocable movement, and when it is driven in a downward direction from its position of FIG. 1, it acts through the links 60 to pivot the contacts 28 in a contact-opening direction about their respective stationary pivots 29. When the crosshead 59 reaches a point near the end of its downward opening stroke, a reset spring 64 acting on the latch 55 drives it clockwise about its stationary pivot 65 into a latching position above a latching roller 66 carried by the crosshead 59.

The latch 55 can be released by driving it in a counterclockwise direction about its pivot 65. This allows the above-mentioned differential pressure acting as a closing bias on the contacts 28 and crosshead 59 to drive the crosshead 59 upwardly, thereby returning these parts to their closed position of FIG. 1.

Resistors shunting main contacts Shunting the right hand pair of main contacts 16, 28 is a voltage-controlling resistor 70, preferably of the form disclosed and claimed in Patent No. 3,074,043McNeir et al., assigned to the assignee of the present invention. The resistor is schematically shown as comprising a resistive ribbon 7 0a helically wound about an insulating core 70b. The insulating core 701) is supported from the conductive stud .15 by means of conductive webs 72 electrically interconnecting the ribbon 70a and the stud 15. The right hand terminal of the resistor 70is electrically connected to the conductive web 72 but the left hand terminal is locally insulated therefrom and is connected by means of a conductor 74 to a stationary electrode 73 of a resistor switch 75.

The resistor switch 75 comprises, in addition to the electrode 73, a second electrode 76 spaced from the electrode 73 and coacting with the electrode 73 to form an interrupting gap between the two electrodes. The second electrode 76 is supported on the conductive housing 33 and is electrically connected thereto at all times. Electrically bridging the two stationary electrodes 73 and 76 is a movable bridging electrode or contact 78, which in its closed position of FIG. 1, butts against the two stationary electrodes or contacts 73 and 76. Thus it will be seen that the right hand resistor 70 is connected in shunt with the right hand main contacts 16, 28 by means, of a circuit that extends through parts 72, 70a, 74, 73, 78, 76 and 33.

As will be apparent from FIG. 1, the left hand set of main contacts 16, 28 is shunted by a similar circuit. Since the parts forming this left hand shunting circuit are substantially identical to those forming the right hand shunting circuit, corresponding parts of the left hand shunting circuit have been assigned corresponding reference numerals.

General description of resistor switch Referring more particularly to the resistor switch 75, it will be noted from FIGS. 1 and 2 that each of the bridging contacts 78 is coupled to a rotatable actuating shaft 80 that is journaled in suitable spaced-apart sup port brackets 81 carried by the tank 12. The coupling of each of the bridging contacts to the shaft 80 is best illustrated in FIG. 2, where an arm 82 is shown keyed to the shaft 80 for rotation therewith. Secured to the arm 82 at its outer end is tubular bushing 83. This tubular bushing is externally threaded and carries :a nut 84 at its upper end that clamps the arm 82 between the nut 84 and a shoulder 85 on the bushing 83. Slidably mounted in the bore of the tubular bushing 83 is a pin 86 that is fixed to the bridging electrode 78. A wipe spring 79 encircles the pin 86 and urges the bridging electrode 78 into firm engagement with the other electrodes 73 and 7-6 of the resistor switch when the switch is in its closed position of FIG. 1 and 2. When the switch is in its normal closed position, the actuating shaft 80 is restrained against counterclockwise movement, as will soon be described. An opening operation is initiated by removing this restraint and rotating the shaft 88 in a clockwise direction, as viewed in FIG. 2. Such a clockwise rotation pivots the arm 82 in a clockwise direction about the axis of shaft 80 and finally drives the bushing 83 upwardly against an abutment 8'7 fixed to the outer end of the pin 86. This drives the pin 86 and the connected bridging contact 78 in an upward direction, thereby separating the bridging contact from the other two contacts or electrodes 73 and 76 to open the resistor switch, The position of bridging contact 78 when fully open is shown in FIG. 3. It will be understood that during the above-described opening operation, the wipe spring 79 maintains the bridging electrode in engagement with the other two electrodes 73 and 76 until the abutment 87 was impacted by the bushing 83. The position of abutment 87 can be adjusted to provide for changes in the point of impact. It is noted that a weight 89 is attached to the outer end of switch arm 82 through bushing 83. The presence of this weight 89 assures that the arm 82 will not be significantly decelerated when its portion 83 impacts against nut 87 to initiate opening movement of the bridging contact 78.

On a closing operation of the resistor switch, the shaft 80 is rotated in a counterclockwise direction from its fully open position of FIG. 3. This drives the arm 82 counterclockwise about the axis of shaft 80, carrying the bridging contact into engagement with the other two contacts 76 and 73. After initial engagement occurs, a predetermined amount of continued counterclockwise movement, or wipe travel, of the arm 82 occurs. This compresses the spring 79 to insure that adequate contact pressure is maintained.

The above-described coupling of each bridging electrode 78 to the rotatable actuating shaft 80 provides for substantially simultaneous opening of the two bridging contacts 78 and substantially simultaneous closing of the two bridging contacts 78.

Resistor switch closing For impart-ing switch closing and switch opening motion to the actuating shaft 80 of the resistor switch, a switch operating mechanism 90, best shown in FIGS, 2, 3 and 4 is provided. This operating mechanism comprises a closing cam 91 that is mounted for rotary or pivotal motion about a stationary pivot '92. Cooperating with this closing cam 91 is a cam follower in the form of a roller 93 mounted on the outer end of a crank 94 that is keyed to the actuating shaft 80. When the closing cam 91 is pivoted in a clockwise direction about the stationary pivot 92 from its fully open position of FIG. 3, the cam 91 forces the follower roller '93 upwardly, pivoting the crank 94, shaft 80, and the switch arm 82 in a counterclockwise direction, thereby driving the bridging contact 78 in a downward closing direction. The position of the parts at the end of this closing operation is shown in FIGS. 2 and 4.

The force for pivoting the closing cam 91 in a clockwise closing direction, as described above, is transmitted to the closing cam through a vertically-reciprooable operating rod 95 that is pivotally connected at its upper end, as indicated at 96, to the closing cam 91. Clockwise closing motion of the cam 91 is effected by driving the rod 95 in a downward direction from its position of FIG. 3 into its position of FIGS. 2 and 4.

For holding the movable bridging contact 78 in its closed position at the end of a closing stroke, a holdclosed latch 98 is provided. This hold-closed latch 98 is pivotally mounted on the same stationary pivot 92 as the closing cam 91 but is freely movable with respect to the pivot 92 and cam 91. A reset spring 99 biases the holdclosed latch 98 clockwise toward its latching position of FIGS. 2 and 4. In this latching position, the latch 98 is positioned beneath a latching roller 100 carried by the crank 94 on the same shaft 101 as the cam follower roller 93 is mounted. When the latch 98 is in this position beneath the latching roller 100, it blocks the crank 94, the shaft 80 and switch arm 82 from moving in a clockwise opening direction.

Resistor switch opening Opening of the resistor switch is effected by releasing the latch 98 to permit switch-opening springs 105 and 106, which are coupled to the shaft 80, to drive the shaft 80 in a clockwise opening direction from its position of FIGS. 2 and 4. As shown in FIGS. 1 and 5, one of these switch-opening springs 105 is a torsion spring encircling the shaft 80, and the other is a compression spring 106 acting on a crank 111 fixed to the shaft 80. The torsion spring 105 urges the shaft 80 in a clockwise direction as viewed in FIG. 5. The other spring 106 urges shaft 80 in the same direction. This spring 106 bears at its rear end on a stop 107 that is mounted on a pivot 108, which is mounted for pivotal motion about a stationary axis. At its front end, the spring 106 bears against a shoulder 109 fixed to a force-transmitting guide pin 110 which is pivotally connected to the crank 111 attached to the shaft 80. The force-transmitting guide pin 110 at its rear end extends through an opening in the stop 107 and pivot 108 and is mounted for free sliding motion in this opening. When the spring 106 discharges, it drives the shoulder 109 and guide pin 110 to the left (in FIG. to help rotate the shaft '80 in a clockwise switch-opening direction.

For controlling the tripping of hold-closed latch 98, a latch-releasing linkage 112 (best seen in FIGS. 2-4) is provided. This latch-releasing linkage comprises a rotatable latch-controlling shaft 116, which is biased in a clockwise direction from its position of FIGS. 2 and 4 by means of a latch releasing spring 118. The latch-controlling shaft 116 is connected to the hold-closed latch 98 by means of a crank 113 keyed to the shaft 116 and a link 114 pivotally connected at its respective opposite ends to the outer end of crank 113 and the hold-closed latch 98.

The latch-releasing spring 118 is a compression spring which acts at its forward end against an auxiliary crank 125 keyed to the latch-controlling shaft 1.16. The connection between the forward end of spring 118 and the auxiliary crank 125 is through a rod 119 fixed to the lower end of the crank 125. This rod 119 has an opening therein through which a guide pin 119a freely extends. This guide pin 119a is fixed to a pivotally mounted stop 121 located at the rear end of spring 118 and is surrounded by the spring 118. The rear end of .the spring 118 bears against the stop 121. When the spring 118 discharges, it expands, acting against the rod 119 to pivot the auxiliary 8 crank 125 and the latch-controlling shaft 116 in a clockwise direction.

Discharge of the latch-releasing spring 118 is controlled by an auxiliary cam 122 rigidly connected to the closing cam 91 through pins 123 of FIG. 4. When the resistor switch is closed as shown in FIGS. 2 and 4, this auxiliary cam 122 holds the latch-controlling shaft 116 in its illustrated position by blocking movement of the auxiliary crank 125 keyed to the latch-controlling shaft 116. An auxiliary cam roller 126 carried by the auxiliary crank 1Z5 bears against the auxiliary cam 122. The auxiliary cam 122 has an idled portion that permits counterclockwise motion of the auxiliary cam from its position of FIGS. 2 and 4 through a substantial angular travel before the auxiliary crank 125 can move clockwise out of its closed position. When the auxiliary cam 122 has been moved through this predetermined angular travel, a sharply inclined portion of its surface passes rapidly beneath the auxiliary cam roller .126, freeing the auxiliary crank 125 and the latch-controlling shaft 116 for clockwise motion. The spring 118 responds to this freeing of crank 125 and shaft 116 by driving the shaft 116 in a clockwise direction, causing linkage 113, 114 to release the hold-closed latch 98 -by pivoting the latch counterclockwise about its pivot 92. When the hold-closed latch 98 is so released, the main resistor switch opening springs 105 and 106 together with contact wipe springs 79 are free to discharge and thus to drive the shaft and switch arms 82 clockwise from their position of FIGS. 2 and 4, thus opening the resistor switch.

Reset of resistor switch operating mechanism during closing It will be recalled that the previously-described closing operation of the resistor switch was effected by driving the closing cam 91 in a clockwise direction about its stationary pivot 92 from its position of FIG. 3 to its position of FIG. 2. Such motion of the closing cam 91 is effected by driving the operating rod in a downward direction from its position of FIG. 3.

When the closing cam 91 is driven in a clockwise closing direction by downward motion of the operating rod 95, it not only imparts closing force to the switch arm 82 through the crank 94 and follower 93 but it also resets the latch-releasing mechanism 112 to permit return of the hold-closed latch 98 to its position of FIGS. 2 and 4. In this connection, the auxiliary cam 122, which is coupled to the main cam 91, rotates in a clockwise direction with the main cam during closing, thereby rotating the auxiliary crank in a counterclockwise direction. This counterclockwise motion of the auxiliary crank .125 recharges the latch releasing spring 118 and also acts through the latch-controlling shaft 116 to drive the links 113 and 114 to the right from their position of FIG. 3. When the link 114 moves to the right in this manner, the torsion reset spring 99 on latch 98 is free to drive the latch clockwise into its reset position of FIGS. 2 and 4.

It will be noted that the coupling between the link 1.14 and the latch 98 is a pin and slot connection. The pin 98a is carried by the latch 98 and the slot 114a by the link 114. When the link 114 moves to the right during switch-closing, the reset spring 99 causes the latch 98 to follow until the latch reaches its latching position against a stop 9811. Thereafter the link 114 continues moving a slight distance further to the right, opening a space between the pin 98a and the right hand end of the slot 114a, as shown in FIG. 4. Adjustment of the length of link .114 will change this spacing and can therefore be used to adjust the latch-release point during a subsequent opening operation.

If, for some unusual reason, the reset spring 99 did not promptly return the latch 98 to its reset position of FIG. 4 when the link 114 moved to the right, as abovedescribed, latch-reset will be effected by back-up reset means. Referring to FIG. 4, this back-up reset means comprises a pin 96a carried by closing cam 91. If the latch 98 does not promptly reset, this pin 96a will engage the latch 98 and force it clockwise into its latching position of FIG. 4 when the closing cam 91 is moved clockwise into its position of FIG. 4 by downward closing motion of operating rod 95.

Actuation of resistor switch operating mechanism during closing For driving the resistor switch operating rod 95 in a downward closing direction from its position of FIG. 3, a compression spring 130 is provided within the tank 12. This compression spring 130 bears at its lower end on the stationary tanks 12 and at its upper end against a shoulder 132 attached to the pivot valve operating rod 52. The pilot valve operating rod 52 is coupled to the resistor switch operating rod 95 through a crank 133 that is pivotally mounted on a stationary pivot 135. One end of the crank .133 is pivotally connected to the pilot valve operating rod 52 at 136, and the other end of the crank 133 is pivotaly connected to the resistor switch operating rod at 137. When the circuit breaker is in open position, the resistor switch closing spring 130 is held in its charged condition of FIG. 3 by a releasable latch 140 (soon to be described). When the latch 140 is released, the closing spring 130 discharges, driving the pilot valve operating rod 52 upwardly, pivoting the crank 133 in a counterclockwise direction, thereby driving the resistor switch operating rod 95 in a downward closing direction.

The above-mentioned latch 140 that controls discharge of the closing spring 130 acts on a force-transmitting linkage 150 which is coupled to the rod 52. This linkage 150 is located at the bottom of the insulator 14 that supports the tank 12 and is at ground potential. The pilot valve operating rod 52 is of insulating material so as to electrically isolate the high voltage portions of the circuit breaker from the ground potential linkage 150. The linkage 150 comprises a plurality of cranks 152, 153 and 154 which are respectively pivoted on stationarily located pivots 152a, 153a and 154a. Interconnecting the cranks 152 and 153 is a link 155 pivotally connected at its opposite ends to the two cranks. Interconnecting the cranks 154 and 153 is a link 156 pivotally connected at its opposite ends to these two cranks. Link 156 is connected to crank 154 by means of a pivot pin 157 that has a portion serving as a latching roller which the latch 140 cooperates with to hold the linkage 150 in its position of FIG. -3.

Closing of the circuit breaker is initiated by suitably tripping the latch 140 of FIG. 3. This is done with a solenoid 158 that, upon energization, drives its armature upwardly to engage the latch 140 and pivot it counterclockwise about its stationary pivot 159 against the bias of a latch reset spring 159a. This removes the restraining efiect of the latch 1-40 from the latching roller 157, permitting the closing spring 130 in the tank 12 to drive the pilot valve operating rod 52 upwardly. Upward movement of the operating rod 52, among other'thin-gs, moves the lower linkage 150 into its position of FIG. 2. A suitable stationary stop 158 is arranged to engage the crank 154 when it enters the position of FIG. 2 and thus prevent movement of the linkage 150 beyond this position.

Releasing the main contacts for closing during resistor switch closing As previously described, this upward movement of the operating rod 52 also acts through parts 133 and 95 to drive the resistor switch closed. In addition, at a point near the end of .the resistor-switch closing operation, the upward movement of operating rod 52 acts to release the latch 55 that was holding the movable main contacts 28 of the circuit breaker open. The previously-described closing bias that had been acting on the movable main contacts 28 responds to tripping of latch 55 by immediately driving the main contacts 28 into their closed position.

The point at which the latch 55 is released is so adjusted that the bridging electrodes 78 of the resistor switches reach closed position appreciably ahead of the instant at which the main contacts 28 of the circuit breaker reach closed position. This results in the resistors 70 being inserted into the power circuit prior to efiective closing of the main contacts 28. This prior insertion of the resistors into the power circuit is occasionally referred to herein as resistor preinsertion.

The means for releasing the latch 55 of the circuit breaker in response to upward movement of the pilot valve operating rod 52 comprises a latch-releasing linkage 160 that is coupled between the crank 133 and the latch 55. This latch-releasing linkage 160 comprises an output arm 163 that is pivotally mounted on a stationary pivot 164. A link 165 interconnects the output arm 163 and the crank 133. This link is pivotally connected at its respective opposite ends to the crank 133 and the output arm 163. When the pilot valve operating rod 52 moves upwardly during the above-described closing operation,

it acts through crank 133 and link 165 to drive the output arm 163 in a clockwise direction about pivot 164, pivoting latch 55 in a clockwise releasing direction about its stationary pivot 65. After a predetermined amount of upward movement of the operating rod 52, the latch 55 is released and the circuit breaker contacts "28 are driven closed by their above-described closing bias.

Coordination between resistor switch opening and main contact opening Opening of the circuit breaker, including the resistor switch, is effected by driving the pilot valve operating rod 52 in a downward direction from its position of FIGS. 1 and 2. As previously explained, this downward motion of rod 52 opens the pilot valve 51 to effect opening of the main contacts 28. Downward motion of rod 52 also produces upward motion of the resistor switch operating rod 95, which trips the hold closed latch 98, as previously described, permitting the resistor switch to open under the influence of its opening springs 105 and 106 and contact wipe springs 79. The point of latch-release for latch 98 is sufficiently delayed to permit the main contacts 28 to have opened well ahead of the point at which the resistor switch is opened.

For driving the pilot valve operating rod 52 downwardly to effect the above-described opening operations, a fluid motor is provided at the end of the lower force transmitting linkage 150. This fluid motor 170 comprises a reciprocable piston 171 that is slidably mounted in a stationary cylinder 172. The piston 171 has a vertically-extending operating rod 177 that can transmit upward force from the piston to a suitable roller 178 carried by the crank 154. When pressurized air is supplied to the cylinder space beneath piston 171, piston 171 moves rapidly upward, pivoting the crank 154 counterclockwise about stationary pivot 154a thereby rapidly pulling the pilot valve operating rod 52 downwardly by force transmitted through the linkage 150.

When the piston 171 reaches the top of its upward pilot valve opening stroke, as shown in FIG. 3, the pressurized fluid beneath it is suitably vented to a low pressure region, and piston 171 quickly returns to its lowermost position of FIG. 2 in response to such venting. This reset position of the piston is shown in dotted lines in FIG. 3. A suitable reset spring 173 is provided to facilitate this piston-resetting operation. The flow of pressurized air into and out of the cylinder space beneath piston 171 is controlled by a suitable three-way valve 175 that in its normal position vents the cylinder space to a low pressure region. When the valve 175 is opened, as by energizing its operating solenoid 176, the valve establishes communication between a high pressure source (not shown) and the cylinder space and also isolates the cylinder space from the low pressure region previously referred to At the. end of the upward opening stroke of the piston 171, valve 175 is returned (by conventional means not shown) to its normal position to vent the cylinder space and permit resetting of piston 171.

It should be apparent that the fluid motor 170 needs to develop only a relatively low force in order to initiate an opening operation. This is the case because this fluid motor does not directly actuate the blast valve member 40 or the main contacts 28 or even the resistor switch electrodes 78. The fluid motor merely operates the small pilot valve 51 and the hold-closed latch 98 of the resistor switch. Operation of the small pilot valve 51 initiates operation of the relatively massive blast valve 40 and contacts 28, and tripping of the hold-closed latch 98 of the resistor switch releases the opening springs 105, 106 of the resistor switch to open the resistor switch. The fact that the forces transmitted through the long rod 52 and linkage 150 during an opening operation are limited to low values enables one to rely upon a relatively lightweight, low-mass construction for these parts, thus contributing to higher speed opening response.

Preinserting the resistors on closing and synchronizing the closing a plurality of resistor switches It has been recognized heretofore that the magnitude of the voltage transients developed upon closing of the circuit breaker can be materially reduced by preinserting a resistor into the power circuit just prior to closing of the main break or breaks of the circuit breaker. In the illustrated circuit breaker, this reduction in voltage is effected by inserting the resistor 70 into the power circuit prior to closing of the main breaks 16, 28.

Where there are a plurality of series-connected resistor switches in a very high voltage power circuit, it is important that all of the resistor switches be closed substantially simultaneously. Otherwise, the inter-contact gap of the last resistor switch to close may be so long that it does not immediately break down in response to the high voltage developed thereacross when the other resistor switches close. This high voltage could cause a damaging arc-over across insulation paralleling this last intercontact gap.

To minimize the chances for such a damaging arc-over, it is important that the closing of all the resistor switches be synchronized with a high degree of precision.

In FIGS. 6 and 7, I have illustrated a circuit breaker in which a plurality of interrupting assemblies, each substantially identical to that shown in FIGS. 1-5, are connected in the power circuit. These interrupting assemblies are electrically connected in series, as is shown in FIG. 7, which is a simplified wiring diagram of the circuit breaker comprising the two interrupting assemblies. These assembles are mechanically coupled together in the manner schematically illustrated in FIG. 6. More specifically, the crank 152 of interrupting assembly I is coupled to the central crank 154 through the previously described linkage 150. Another linkage, also designated 150 for convenience, is used for coupling crank 152 of interrupting assembly II to the central crank 154. This latter linkage 150 comprises a link 155 pivotally connected at its respective opposite ends to the crank 152 and 154. A pivot pin 199 provides the pivotal connection between the central crank 154 and this link 155. In the crank 154, the effective distance d between central axis of central pivot 154a and the pivot 157 is so related to the effective distance 1 between the axis of central pivot 154a and the pivot pin 199 that the vertically extending rods 152 move in unison through the same travel distance when the central crank 154 is rotated between the positions of FIGS. 2 and 3.

Each interrupting assembly is substantially identical, and when the circuit breaker is open, both assemblies are latched in their open position by a latch corresponding to the latch 140 of FIG. 3. When the latch 140 is tripped as hereinabove described, the springs 130 in the tank 12 of each assembly are free to drive their associated resistor switches closed. Each of these springs 130 acts through its associated linkage 133, 95, 91, 93 to impart closing motion to its associated resistor switch arm 82. At an intermediate point in the closing operation, the linkage 133, 95, 91, 93 acts through another linkage 165, 163 to release the latch 55 holding the main contacts 28 open, whereupon the previously described pneumatic bias acting on these contacts 28 drives them into closed position. The point in the resistor switch closing stroke at which each of the latches 55 is tripped is so adjusted that the main contacts 28 do not reach closed position until appreciably after the resistor switch contacts have engaged.

There are a number of features which enable the series-connected resistor switches to reach closed position substantially simultaneously, thereby reducing the chance of a damaging arc-over across the insulation paralleling the last resistor switch to close. One of these features is the fact that the resistor switch operators 130, 52, 133, 95 in the high voltage tanks 12 are mechanically coupled together (through the mechanical link comprising parts 52, linkages 150 and central crank 154) and are controlled by a single latch (140) common to both operators. The use of a common latch assures that the two closing springs will be freed to begin their respective closing operations at the same instant. The mechanical link between the two switch operators forces the two operators to move their closing cams 91 at substantially the same speed. If one closing cam 91 tends to move slightly faster than the other, this mechanical link pulls the other carn along to substantially equalize the speed of the two closing cams. In this latter regard, it will be recalled that the linkages 150 and crank 154 are designed to provide for equal travel of the two rods 52 when the crank 154 rotates, as it would when the latch is released.

It should be noted that the main driving force for closing each resistor switch is transmitted from spring 130 through a relatively short driving linkage, which comprises a short length of rod 52, crank 133, rod 95, cam 91, and follower 93. The only portion of this short linkage which does not have a high resistance to buckling when loaded in compression is the relatively slender rod 95 This characteristic of rod 95 does not detrimentally affect the closing operation because the rod 95 is loaded, not in compression, but in tension during closing. While it is true that rod 95 is loaded in compression during an opening operation, there is no significant buckling problem then because only small forces compared to the resistor switch-closing forces are transmitted through the rod 95 during opening. This is the case because only the forces needed to trip the resistor switch latch 98 are transmitted through the rod 95 during a circuit breakeropening operation. These forces are low in comparison to the switch-closing force which is relied upon to recharge the relatively heavy opening springs, 105, 106 for the resistor switch.

Synchronizing the opening of a plurailty of resistor switches During an opening operation it is important that the resistor switches be opened substantially simultaneously in order to distribute across all of the resistor switches the high magnitude recovery voltage developed during interruption of the resistor current. If this high magnitude voltage is impressed across only a single resistor switch, which may have opened prematurely, it is likely to cause a delayed breakdown, or restrike, which could lead to the development of excessive overvoltages.

In the circuit breaker illusrtated in FIGS. 6 and 7, there are a number of features which contribute to attainment of the desired high degree of synchronization in the opening operations of the resistor switches. One of these features is that the two mechanisms (91, 122, 125, 116, 113, 114) for releasing the latches 98 in the two interrupting assemblies are mechanically connected together through a 13 linkage comprising parts 95, 133, 52, and 150 of interrupter assembly I, central crank 154, and parts 150, 52, 133 and 95 of interrupter assembly II. This mechanical interconnection, which, as previously pointed out, is designed to compel equal movement of rods 52, assures that these latch-releasing mechanisms will operate in unison.

A related feature that contributes to simultaneous operation of the latch-releasing mechanisms is that a single common operator, in the form of fluid motor 170, is used foractuating the two latch-releasing mechanisms during an opening operation. This, together with the above-noted mechanical interconnection, assures that operation of the two latch-releasing mechanisms will be initiated at substantially the same instant during the opening operation.

It is noted that the forces transmitted from the fluid motor 170 to the latch-releasing mechanisms 91, 122, 125, 116, 113, 114 incident to an opening operation load the operating rods 52 in tension and not in compression. Although these opening forces are relatively low, these rods 52 are so long and slender that buckling could be a problem if these rods were loaded in compression, even by these relatively low forces. I am able to eliminate this problem by applying the opening forces to the rods 52 as tensile forces. Note also that the opening forces are applied to rods 155 and 156 as tensile forces.

In a number of prior circuit breakers, the resistor switch opening has been controlled by opening motion of the main contacts or a part that moves with the main contacts. For example, at a predetermined point in the opening stroke of the main contacts, a resistor switch latch has been tripped by the main contacts or by a part coupled to the main contacts to initiate resistor switch-opening. This prior approach is not sufliciently precise for those applications that require a high degree of synchronism in the opening of several resistor switches, because the instant at which opening motion of each of the resistor switches begins is dependent upon the opening speed of the main contacts. This main contact-opening speed is subject to variations which, in some cases, are not reflected in the opening speed of all the main contacts. For example, diiferences may develop in the pressure of the actuating fluid in the various interrupting assemblies or differences may develop in the frictional loads on the contracts in the various interrupting assemblies. These differences could result in one set of main contacts moving at a significantly different speed from another. If resistor switch-opening is initiated by motion of the main contacts, then these main contact-opening speed differences would initiate opening of the various resistor switches at ditferent times, thus detrimentally affecting the desired opening-synchronization between the resistor switches.

The disclosed arrangement for controlling the resistor switches is not affected by variations in the opening speed of the main contacts. This is the case because the resistor switches are operated to open independently of main contact motion. The resistor switch opening springs 105 and 106 which provide the energy for opening the resistor switch contacts are controlled by a linkage connected directly to the common fluid motor 170. When the fluid motor 170 is operated from its position of FIG. 2 to that of FIG. 3, opening of the resistor switches is initiated, irrespective of the speed at which the main contacts move toward their fully open position in response to the opening of pilot valve 51, which also results from this operation of fluid motor 170. Eliminating the reliance upon main contact motion eliminates any variations resulting from variations in speed of the main contacts and thus makes it possible to achieve more precise synchronism between the resistor switches during their opening operations.

Adjustment for changing the starting point for resistor switch opening It is to be noted that adjustments can be made in the instant at which opening of a given resistor switch is to be initiated 1) by varying the effective length of the link 114 in the latch-releasing mechanism for resistor switch latch 98, or (2) by suitably varying the initnal charge of latch-releasing spring 118. The availability of such adjustments provides for a much wider and more effective control of the starting point for resistor switch-opening than has been provided by prior arrangements that relied upon main contact opening to initiate resistor switch-opening. In these latter arrangements, adjustments were made by varying the point in the main contact opening stroke at which the resistor switch latch was tripped. But the main contact-opening stroke in the disclosed circuit breaker is normally so fast that changes in the point of this opening stroke at which resistor switch-tripping occurred would product only very slight changes in the time instant at which tripping occurs. In other words, the main contact opening time is so short that it offers little to Work with as a means for adjusting the resistor switch openinginstant.

It is to be further noted that the above adjustments in the length of link 114 or the compression of spring 118, although they vary the resistor switch opening point, do not affect the resistor switch closing characteristics. Closing forces are transmitted to the resistor switch contact arm 82 directly through the closing cam 91 and follower 93 without being affected by adjustments of the latchreleasing mechanism 112-120 for latch 98. Also, the above-described adjustments in the latch-releasing mechanism do not affect any adjustments that might have been made in contact-wipe by changing the position of nut 87 on the resistor switch bridging contact 78.

Still further, it is to be noted that the above-described adjustments in the latch-releasing mechanism, although they vary the starting instant for resistor switch opening, do not change the speed of motion of the movable resistor switch contact 78. Thus, this speed of motion can be set to a desired optimum value and will remain unchanged despite adjustments of parts 114 or 118 that change the starting point at which resistor switch opening motion begins.

Another factor that controls the length of the time interval preceding tripping of the hold-closed latch 98 of the resistor switch is the mass of the auxiliary crank 125. By making this mass relatively large, I can lengthen the time required for the springs 118 to drive the link 114 into latch-releasing engagement with latch 98, thus lengthening this time interval to the desired extent.

Additional features facilitating synchronization of resistor switches on opening The opening springs 105, 106 for each resistor switch are quite large to provide for very high opening speeds of the resistor switch contacts once the hold-closed latch 98 is tripped. This high opening speed permits resistor switch-opening to be initiated at a later point following initiation of main contact opening than would be possible with lower resistor switch speeds. Such delaying of the starting point for resistor switch opening is particularly advantageous for those opening operations that immediately follow a closing operation. In this connection, it should be pointed out that the impact resulting from termination of a resistor switch-closing operation will cause the resistor switch arm 82 to bounce back and forth slightly. Even though a dashpot (not shown) is present, a certain minimum time is needed for these oscillations to be completely damped out to permit arm 82 to reach a completely at-rest condition. By delaying the opening operation of the resistor switches, as above-described, a sufficient time is made available after a closing operation and'before resistor switch-opening for these oscillations to be substantially completely damped out. Accordingly, when a resistor switch-opening operation is initiated, the velocity of the arm 82 at the point of latch release will be substantially zero. If the above-described oscillations had persisted until this instant, the arm 82 would have had an initial velocity, rather unpredictable in magnitude and direction, at this instant. Such initial velocity could materially alfect the distance that the arm 82 could be moved in a given period following latch tripping, and could thus interfere with the desired synchronization of the resistor switch-opening operations.

It is to be noted that preinsertion of the resistors on closing also lengthens the time available for the arm 82 to settle down to an at-rest condition before opening might be initiated. Thus, such resistor preinsertion during closing facilitates synchronizing of the opening of the resistor switches during an immediately-following opening operation. The time available to begin resistor switch-opening varies directly with the length of time that the circuit breaker has available to interrupt the circuit. If the circuit breaker is rated for very short interrupting times, for example, two cycles, the time available to begin resistor switch-opening is correspondingly short. In such short interrupting time breakers, the time available for the arm 82 to settle down to an at-rest state after closing is especially short when the breaker must be opened immediately following such closing. But the high speed opening characteristics of my resistor switch permit a sufiicient delay in the starting point for resistor switch-opening to allow sufiicient time after closing for the arm 82 to settle down to its at-rest condition, even in a two cycle interrupting time breaker.

Polyphase circuit breakers In the above description, I have described only a single phase of the circuit breaker. It is to be understood that for a polyphase circuit breaker, identical interrupting assemblies are provided in each phase of the circuit breaker. These interrupting assemblies in the different phases are rigidly mechanically tied together by suitable means, which I have depicted schematically in FIG. 6 as a rigid shaft 200 shown in dotted lines. This shaft 200 is shown as a continuation of pivot 154a. For schematic purposes, this shaft 200 is shown keyed to the crank 154 and extending between the different phases of the breaker. The shaft 200 is keyed to a central crank 154 in each adjacent phase, such crank corresponding to the central crank 154 shown in solid line form. Thus, all the central cranks 154 are tied together for movement in unison. The central crank 154 in each adjacent phase is coupled to the interrupting assemblies of that phase in the same manner as depicted in the illustrated phase, i.e., by linkages such as l The interrupting assemblies in the different phases of a circuit breaker must also be synchronized with a rather high degree of precision (because of known electrical considerations). It will be apparent that the positive mechanical tie (200) between the linkages 150 in these different phases will provide for such synchronization. In a preferred form of the invention, a single latch 140, common to all three phases, is relied upon for controlling the three phases of the circuit breaker, i.e., for initiating simultaneous closing of the three phases. This common control further contributes to the desired high degree of synchronization between the phases. With the mechanical tie present between the phases, it is possible to use a separate fluid operator, such as 170, for each phase, assuming the fluid operators are suitably synchronized; but in some cases, I may use only a single operator 170 common to all phases.

Although I have specifically described a circuit breaker that has two interrupting assemblies electrically connected in series in each phase, it is to be understood that the invention is also applicable to circuit breakers that have fewer or more interrupting assemblies per phase. Where there are more interrupting assemblies per phase, one or more additional linkages, each being of a design such as shown in dotted lines at 150a in FIG. 6, can be tied to the linkages 150 shown.

Where there is only one interrupting assembly per phase, the positive mechanical tie between the linkages 156 in the respective phases will provide the desired precise synchronization between the single interrupting assemblies of the three phases. This positive mechanical tie can be through means such as the rigid shaft 200 of FIG. 6. Alternatively, the interrupting assemblies I and II of FIG. 6 can be located in different phases, in which case, the linkages that are shown in solid lines would be used for mechanically tying together the interrupting assemblies of the two phases. The third phase would be mechanically tied to these two phases with the additional linkage 15011 of FIG. 6.

While I have shown and described particular embodiments of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention in its broader aspects; and I, therefore intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric circuit breaker comprising:

(a) a tank adapted to be at a high voltage with respect to ground,

(b) a main break comprising separable main contacts within said tank,

(c) a resistor shunting said main break,

(d) a resistor switch within said tank and having a break in series with said resistor and in parallel with said main break,

(e) said resistor switch break comprising a pair of separable contacts, one of which is movable,

(f) opening bias means for biasing said movable resistor switch contact toward an open position,

(g) a resistor switch latch located within said tank for restraining said movable resistor switch contact in said closed position and releasable to permit said opening bias means to drive said movable resistor switch contact toward open position,

(h) latch-releasing means comprising a controlling member located within said tank and free from positive mechanical connection with said main contacts, said latch-releasing means being operable to eff ct release of said resistor switch latch when said controlling member is driven through a predetermined stroke,

(i) a mechanical linkage for controlling said resistor switch latch coupled to said controlling member and extending from a control point at substantially ground potential to said controlling member for driving said controlling member through said predetermined stroke when said linkage is actuated,

(j) operation-initiating means for said main break operable in response to said actuation of said linkage for initiating an opening operation of said main break,

(k) and main break-operating means responsive to operation of said operation-initiating means for opening said main break at a point substantially prior to separation of said resistor switch contacts.

2. The circuit breaker of claim 1 in which said latchreleasing means and said linkage are operable to cause opening of said resistor switch 'at a time after said linkage is first actuated that is independent of the speed at which said main break operating means opens said main break.

3. The circuit breaker of claim 1 in combination with means for varying the time required for said latch-releasing means to release said latch after said controlling member has been driven through said predetermined stroke.

4. The circuit breaker of claim 1 in combination with:

(a) closing means for imparting closing force to said movable resistor switch contact,

(b) means for coupling said closing means to said linkage for effecting closing of said resistor switch when said linkage is actuated in an opposite direc- 17 tion to the direction for producing resistor switchp n and means responsive to actuation of said linkage in said opposite direction for initiating a closing operation of said main break.

5. An electric circuit breaker interrupting assembly comprising:

(a) a tank adapted to be at a high voltage with respect to ground,

(b) a main break within said tank,

(c) a resistor shunting said main break,

(d) a resistor switch within said tank and having a break in series with said resistor and in parallel with said main break,

(c) said resistor switch break comprising a pair of separable contacts, one of which is movable,

(f) opening bias means for biasing said movable resistor switch contact toward an open position,

(g) a latch located within said tank for restraining said movable resistor switch contact in said closed condition and releasable to permit said opening bias means to drive said movable resistor switch contact toward open position,

(h) a mechanical linkage for controlling said resistor switch latch extending from a control point at substantially ground potential to the region of said latch,

(i) means operable independently of the opening speed of said main break for releasing said latch when said mechanical linkage is actuated,

(j) opening-operation-initiating means for initiating an opening operation of said main break in response to latch-releasing actuation of said mechanic-a1 linkage,

(k) and main break-opening means responsive to operation of said opening-operation-initiating means for opening said main break at a point substantially prior to separation of said resistor switch contacts.

6. The circuit breaker of claim 5 in which said mechanical linkage operates to effect release of said latch in a time after said linkage is first actuated that is independent of the speed of operation of said main break.

7. An electric circuit breaker comprising:

(a) two spaced-apart interrupting assemblies, each constructed as defined in claim 5,

(b) the tanks for the two assemblies being at different voltages with respect to each other when the circuit breaker is open,

(c) actuating means for said two linkages for controlling opening of said circuit breaker,

(d) and means comprising a mechanical interconnection between said two linkages for causing said actuating means to actuate said linkages substantially simultaneously and thereby to produce substantially simultaneous opening of said resistor switches.

8. The circuit breaker interrupting assembly of claim 5 in combination with:

(a) closing means Within said tank for imparting closing force to said movable resistor switch contact, (b) means for coupling said closing means to said linkage for effecting closing of said resistor switch when said linkage is actuated in an opposite direction to the direction for producing resistor switch-opening,

(c) closing bias means within said tank for actuating said linkage in said opposite direction,

(d) releasable restraining means for preventing said closing bias means from actuating said linkage until said restraining means is released.

9. An electric circuit breaker comprising:

(a) two interrupting assemblies, each constructed as defined in claim 5,

(b) the tanks for the two assemblies normally being at ditferent voltages with respect to each other when the circuit breaker is open,

(c) each interrupting assembly further comprising:

(i) closing means within said tank for imparting 18 closing force to said movable resistor switch contact,

(ii) means for coupling said closing means to said mechanical linkage of claim 5 for effecting closing of said resistor switch when said mechanical linkage is actuated in an opposite direction to the direction for producing resistor switch-open- 111g,

(iii) closing bias means within said tank for actuating said mechanical linkage in said opposite direction,

(1?) means for mechanically connecting said two mechanical linkages together,

(g) and releasable restraining means for preventing the closing bias means within said tanks from actuating said mechanical linkages in said opposite direction until said restraining means is released.

10. An electric switch comprising:

(a) a contact movable from a closed position to a fully-open position,

(b) means biasing said contact towards said fully-open position,

(c) a latch for restraining said contact in said closed position and releasable to permit said biasing means to drive said contact toward said fully-open position,

((1) a closing cam movable from a normal position to an operated position to supply the force for driving said contact into closed position,

(e) means for driving said contact from said fullyopen position to said closed position in response to motion of said closing cam from said normal to said operated position,

(f) means for returning said cam to said normal position,

(g) latch-releasing means controlled by return motion of said cam to said normal position for releasing said latch after a predetermined amount of said return motion of the cam, to then initiate opening motion of said contact.

11. The switch of claim 10 in which said closing cam is mounted for rotary motion, is movable in one direction of rotation from a normal position to an operated position to supply the force for driving said contact into closed position, and is movable in an opposite direction of rotation during said return motion.

12. The electric switch of claim 10 in combination with:

(a) latch-biasing means for restoring said latch to a position for restraining said contact in closed position when said contact is moved into closed position,

(b) and means positively coupled to said closing cam for transmitting a force from said cam to said latch that acts to force said latch into its contact-restraining position in the event that said latch-biasing means is effective in restoring said latch to its contact-restraining position.

13. The switch of claim 10 in which latch-releasing means comprises:

(a) a latch-releasing spring,

(b) a linkage connected between said latch-releasing spring and said latch for releasing said latch in response to discharge of said latch-releasing spring, and

(c) means for preventing said latch-releasing spring from discharging during initial return movement of said cam and for permitting said latch-releasing spring to discharge when said cam has traveled through a predetermined return travel.

14. An electric circuit breaker comprising:

(a) a plurality of tanks adapted to be at a high voltage with respect to ground,

(b) main breaks, each comprising separable main contacts respectively located within said tanks,

(c) resistors respectively shunting said main breaks.

(d) a plurality of resistor switches respectively located within said tanks and having breaks respectively connected in series with said resistors,

(e) each of said resistor switches comprising a pair of separable contacts, one of which is movable, (f) a plurality of biasing means for the respective resistor switches located at the respective tanks for biasing the movable contact of the associated resistor switch toward engagement with the other contact when said circuit breaker is open,

(f') force-transmitting means between each of said biasing means and its associated movable resistorswitch contact for transmitting switch-closing force between said biasing means and said associated movable resistor-switch contact,

(g) a plurality of linkages respectively coupled to said force-transmiting means and extending to points at substantially ground potential,

(g') said linkages and said force-transmitting means being free to move independently of said main contacts without transmiting force to said main contacts,

(h) means at substantially ground potential for mechanically connecting said linkages together,

(i) means including releasable restraining means for said plurality of linkages and at substantially ground potential for preventing said biasing means from operating to drive their respective associated movable contacts into closed position until said restraining means is released, and

(j) means for releasing said restraining to initiate substantially simultaneous closing of the movable contacts of said resistor switches.

15. The circuit breaker of claim 14 in which:

(a) one of the main contacts of each of said main breaks is movable,

(b) main biasing means associated with each main break is provided for biasing the movable main contact of said main break toward closed position,

() releasable latching means individual to each tank is provided for restraining said movable main contact in an open position when said circuit breaker is open, and

(d) means controlled by a closing operation of said resistor switches is provided for releasing said latching means at a predetermined point in a resistor switch closing operation to then permit said main biasing means to drive its associated movable main contact closed.

16. The circuit breaker of claim 15 in which said latching means is released at an instant that results in said movable main contact reaching closed position appreciably after said movable resistor switch contact reaches closed position.

17. The circuit breaker of claim 14 in combination with means controlled by a closing operation of said resistor switches for initiating closing of said main breaks at a predetermined point in a resistor switch-closing operation after said resistor-switch closing operation has begun.

18. The circuit breaker of claim 17 in which closing of said main break is initiated at an instant that results in said main break being etfectively closed appreciably after said movable resistor switch-contact reaches closed position.

19. An electric circuit breaker comprising:

(a) a plurality of tanks adapted to be at a high voltage with respect to ground,

(b) main breaks respectively located within said tanks,

(0) resistors respectively shunting said main breaks,

(d) a plurality of resistor switches respectively located within said tanks and having breaks respectively connected in series with said resistors,

(e) each of said resistor switches comprising a pair of separable contacts, one of which is movable,

(t) a plurality of biasing means [or the respective resistor switches located at the respective tanks for biasing the movable contact of the associated resistor switch toward engagement with the other contact when said circuit breaker is open, t

(g) a plurality of linkages respectively coupled to said biasing means and extending to points at substantially ground potential,

(h) means at substantially ground potential for mechanically connecting said linkages together,

(i) means including releasable restraining means for said plurality of linkages and at substantially ground potential for preventing said biasing means from operating to drive its associated movable contact into closed position until said restraining means is released,

(j) means for releasing said restraining means to initiate substantially simultaneous closing of the movable contacts of said resistor switches,

(k) force-transmitting means between each of said biasing means and its associated movable contact for transmitting switch-closing force between said biasing means and said movable contact when said restraining means is released,

(1) said force-transmitting means comprising a closing cam coupled to said biasing means and a follower coupled to said movable contact, said closing cam being movable from a normal position to an operated position during a switch-closing operation of said biasing means,

(m) means for returning said came to its normal position when said circuit breaker is operated to open position,

(n) releasable auxiliary latching means for holding said movable contact in closed position during a portion of the return movement of said cam,

(0) means for releasing said auxiliary latching means at a predetermined point in an opening operation of said main breaks,

(p) and means responsive to release of said auxiliary latching means for driving said movable resistor switch contact into open position.

20. An electric circuit breaker comprising:

(a) a plurality of tanks adapted to be at a high voltage with respect to ground,

(b) main breaks, each comprising separable main contacts, respectively located within said tanks,

(c) resistors respectively shunting said main breaks,

((1) a plurality of resistor switches respectively located within said tanks and having breaks respectively connected in series with said resistors,

(e) each of said resistor switches comprising a pair of separable contacts, one of which is movable,

(f) a plurality of biasing means for the respective resistor switches located at the respective tanks for biasing the movable contact of the associated resistor switch toward engagement with the other contact when said circuit breaker is open,

(f) force-transmitting means between each of said biasing means and its associated movable resistorswitch contact for transmitting switch-closing force between said biasing means and said associated movable resistor-switch contact,

(g) a plurality of linkages respectively coupled to said force-transmitting means extending to points outside said tanks,

(g') said linkages and said force-transmitting means being free to move independently of said main contacts without transmitting force to said main contacts,

(11) means for mechanically connecting said linkages together,

(i) means including releasable restraining means for said plurality of linkages and at substantially ground potential for preventing said biasing means from operating to drive its associated movable contact into 21 22 closed position until said restraining means is re- References Cited leased, and (j) means for releasing said restraining means to initi- UNITED STATES PATENTS ate substantially simultaneous closing of the movable 2 911 54 11 1959 o l 2 14 contacts of said resistor switches. 5 3 150 245 9 19 4 Leds et 1 200 14 21. The circuit breaker of claim 19 in combination with 3 291 947 12 1966 Van Sickle 2 143 means controlled by a closing operation of said resistor switches for initiating closing of said main breaks at a ROBERT S. MACON, Primary Examiner. predetermined point in a resistor switch-closing operation. 

